A calcium dependent protein kinase involves H2O2 mediated guard cell signaling in Aarabidopsis

Drought is a major threat for plant growth and productivity. Plants lose over 90% of water by transpiration through stomatal pores. The cytosolic free Ca2+ elevated in guard cells in response to stress stimuli triggers stomatal closure. The plant-specific calcium-dependent protein kinases (CDPKs) play important roles in regulating downstream components of calcium signaling. In this study the biological function of Arabidopsis calcium dependent protein kinase, CPK8, in response to ABA signaling in guard cells was characterized. The plants of TDNA insertion mutant of cpk8 were more sensitive to drought stress than wild-type plants. The GUS staining studies confirmed that CPK8 expressed in leaves, specifically in guard cells. RT-PCR analysis showed that CPK8 expression was induced in response to drought stress. Further, pre-opened cpk8 stomata failed to close in response to H2O2 and Ca2+, which is consistent with the inability of cpk8 plants to reduce water loss upon drought. The drought susceptibility and stomatal impairment in response to H2O2 and Ca2+ of the cpk8 implicated that CPK8 plays a role in cellular environment in the control of H2O2 homeostasis and also as a compulsory molecule in the transduction of H2O2 signal in guard cells in response to drought stress.